Innovative potential of additive friction stir deposition among current laser based metal additive manufacturing processes: A review

Industry 4.0 being the new face of manufacturing for future, metal additive manufacturing is a key element in this framework. For metal additive manufacturing, laser-based additive manufacturing techniques are dominating today. However, some of the inherent technical limitations associated with these techniques lead to a significant gap between the industrial requirements and the final deliverables. Additive friction stir deposition is a promising alternative that is still in its early stages of development. This review summarizes the vital findings in AFSD with particular emphasis on microstructure evolution and physical properties. The technical limitations of laser-based AM techniques are discussed to describe the role of AFSD in their domain. AFSD is discussed sequentially covering the basic physical process, features, capabilities, and limitations. AFSD, being a solid-state thermomechanical process, results in a refined equiaxed microstructure with enhanced mechanical properties and no signs of porosity and residual stresses. In addition to this, AFSD is capable of depositing large scale components at a high build rate that leads to cost and energy-efficient fabrication. The existing limitations of the process are discussed with the scope for future improvements. This critical review concludes with the suggested strategies for the widespread adoption of AFSD. (C) 2020 CIRP.